Among the conventionally-known power conversion apparatus are ones in which a plurality of cooling units (hereinafter referred to as “power conversion units”) are accommodated within an apparatus casing with respective cooling fins of the plurality of cooling units disposed opposed to one another, and in which cooling air is supplied to between the opposed cooling fins. In such power conversion apparatus, semiconductor devices (hereinafter referred to as “conversion devices”) are mounted on respective mounting surfaces of the power conversion units, and heat of the conversion devices is transmitted to the cooling fins.
Heat of the conversion devices transmitted to the cooling fins can be cooled efficiently by the cooling air supplied to between the opposed cooling fins (see, for example, Japanese Patent No. 5355822). By the heat of the conversion devices (i.e., power conversion units) being cooled with the opposed cooling fins as noted above, it is possible to reduce the weight and size of the power conversion apparatus.
In such conventionally-known power conversion apparatus, a portion of the heat produced by the conversion devices is radiated directly from the respective surfaces of the conversion devices to the interior space of the casing. Further, other heat-producing sources than the power conversion units are disposed dispersedly in the interior of the power conversion apparatus. Thus, temperature in the interior of the casing may undesirably increase due to the heat radiated directly from the surfaces of the conversion devices to the interior space of the casing and the heat radiated from the heat-producing sources to the interior space of the casing.
Therefore, a technique is presently required for maintaining at suitable temperature the surfaces of the conversion devices and the heat-producing sources disposed dispersedly in the interior of the casing. However, with the power conversion apparatus disclosed in the above-identified U.S. Pat. No. 5,355,822, where the cooling air is supplied to between the opposed cooling fans, it is difficult to cool the entire interior space of the casing, and thus, it is difficult to maintain at suitable temperature the surfaces of the conversion devices and the heat-producing sources disposed dispersedly in the interior of the casing.
Further, in recent years, portable power conversion apparatus for mounting on a vehicle have been proposed, and thus, there has been an increasing demand for a lighter and more compact portable power conversion apparatus, i.e. a portable power conversion apparatus of a reduced weight and size. As one approach for reducing the weight and size of the portable power conversion apparatus, it is conceivable to narrow, or reduce the size of, the interior space of the casing. However, such an approach would further increase the necessity for maintaining at suitable temperature the surfaces of the conversion devices (power conversion units) and the heat-producing sources disposed dispersedly in the interior of the casing